pattern.go

// pattern.go
package main

import (
	"fmt"
	"regexp"
	"strconv"
)

func main() {
	searchIn := "John: 2578.34 William: 4567.23 Steve: 5632.18" // string to search
	pat := "[0-9]+.[0-9]+"                                      // pattern search for in searchIn

	f := func(s string) string {
		v, _ := strconv.ParseFloat(s, 32)
		return strconv.FormatFloat(v*2, 'f', 2, 32)
	}

	if ok, _ := regexp.Match(pat, []byte(searchIn)); ok {
		fmt.Println("Match found!")
	}

	re, _ := regexp.Compile(pat)
	str := re.ReplaceAllString(searchIn, "##.#") // replace pat with "##.#"
	fmt.Println(str)
	// using a function :
	str2 := re.ReplaceAllStringFunc(searchIn, f)
	fmt.Println(str2)

}

/* Output:
Match found!
John: ##.# William: ##.# Steve: ##.#
John: 5156.68 William: 9134.46 Steve: 11264.36
*/